Molecules: two or more “atoms” “bonded” together. (Brooker, 27) Can be the same atom or different atoms. Often used interchangeably with “compounds.” Humans are primarily made of 'CHNOPS' which includes "carbon," “hydrogen," "nitrogen," "oxygen," "phosphorus," and "sulfur." (Norman, 6/11/09) Adjective - ‘molecular.’

The “cell”… is essentially a bag having a stiff outer wall to give it strength. Inside the bag we find a good number of very large molecules and many rather small ones. There may be perhaps several thousand different kinds of large ones and perhaps a similar number of small ones. It is one of the interesting generalizations of biochemistry that relatively few medium-size molecules are made by living things. (Crick, 34)

Amphipathic: molecule with “hydrophilic” and “hydrophobic” regions. For example, ‘carrier molecule.’ (Norton Lectures, 6/3/09)

Cholesterol: a short and fairly rigid molecule that is produced by animal cells. Cholesterol tends to stabilize membranes; its effects depend on "temperature." At higher temperatures, such as those observed in mammals that maintain a constant body temperature, cholesterol makes the membrane less fluid. At lower temperatures, such as in icy water, cholesterol makes the membrane more fluid and prevents it from freezing. (Brooker, 89)

Esters: sweet-smelling compounds found in perfumes and in fruit flavors. (Hunt, 143)

Hydrophilic: molecules that will dissolve in water. (Brooker, 34) Water loving. Water "soluble." Similar to water. (Norman, 6/2/09)

Hydrophobic: molecules composed predominantly of carbon and hydrogen that are relatively "insoluble" in water. (Brooker, 34) Water fearing. Unlike water. For example, vegetable oil. (Norman, 6/2/09)

Isomers: structures with identical (chemical or) molecular formulas but different structures and characteristics. (Brooker, 44)

Macromolecules: large molecules composed of many molecules bonded together. "Carbohydrates," "lipids," “proteins,” and “nucleic acids” are important macromolecules found in living organisms (Brooker, 4)

Molecular Structure: the location of the atoms, groups or "ions" relative to one another in a molecule, as well as the number, type and location of “covalent bonds.” (MeSH)

Pigment: a colored substance. A wide variety of different chemicals form pigments, and these pigments have many different functions in living organisms. (Indge, 208) Having different pigments allows plants to absorb "light" at many different "wavelengths." In this way, plants are efficient at capturing the energy in sunlight. A molecule that can absorb light energy. When light strikes a pigment, some of the wavelengths of light energy are absorbed, while others are reflected. We perceive that leaves are green because they are reflecting energy of the green wavelength. Various pigments in the leaves absorb the other light energy wavelengths. A white object reflects nearly all of the light energy falling on it, whereas a black object absorbs nearly all of the light energy. In the visible "electromagnetic spectrum," light energy is usually absorbed by ‘boosting’ electrons to higher energy levels. (Brooker, 157) Also referred to as 'pigment molecules.'

Carotenoids: yellow, red or brown pigments found in plants. Carotenoids occur in flowers such as wallflowers and in fruits such as tomatoes where they contribute to the bright colors responsible for attracting insects for pollination and/or birds for dispersal. (Indge, 51) These pigments impart a color that ranges from yellow to orange to red. Often the major pigments in flowers and fruits. As the quantity of "chlorophyll" in the leaf declines during autumn, the carotenoids become readily visible and produce the yellow and oranges of autumn foliage. (Brooker, 155)

Chlorophyll: pigments that give plants their green color. (Brooker, G-152) The green pigments found in organisms which are responsible for the capture of light energy. (Indge, 58) They absorb light most strongly in the red and violet parts of the visible electromagnetic spectrum and absorb green light poorly. (Hence, more green light is reflected to our eyes.) (Brooker, 155)

Melanin: a pigment that gives color to skin and eyes and helps protect it from damage by ultraviolet light. (NCIt)

Phycocyanins: any of the various blue photosynthetic pigments in blue-green algae. (Oxford)

Polar: involving or pertaining to the separation of positive and negative electric change between parts of a molecule. (Oxford)

Polar Molecules: molecules containing significant numbers of “polar bonds.” (Brooker, 29) Have polar bonds which do not cancel each other out, so that the whole molecule is polar. (Hunt, 281)

Polymer(s): a chain of chemical building blocks. (Lewis, 175) Extremely large macromolecules being composed of thousands or even millions of atoms. Formed by linking together many smaller molecules. Meaning ‘many small parts.’ (Brooker, 44) There are three biologically important groups of polymers found in living organisms: “nucleic acids,”  “polysaccharides,” and “proteins.”

Dimer: two “monomers” bound together by "dehydration synthesis." (Norton Lectures, 6/16/09)

Monomer: one of the similar small molecules that join together to form a polymer. There are three important biological monomers:  “monosaccharides,” “amino acids,” and “nucleotides.” (Indge, 177)